pISSN 1229-845X, eISSN 1976-555X J. Vet. Sci. (2014), 15(4), 557-561 http://dx.doi.org/10.4142/jvs.2014.15.4.557 Received: 5 Sep. 2013, Revised: 7 May 2014, Accepted: 19 Jun. 2014

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Veterinary Science

Original Article

Determining the age of cats by pulp cavity/tooth width ratio using dental radiography Kyoungsun Park, Jaesang Ahn, Sunmee Kang, Euiri Lee, Soohyun Kim, Sangwan Park, Sungwon Park, Hyunwoo Noh, Kangmoon Seo* Research Institute for Veterinary Science, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea The purpose of this study was to evaluate the effect of age on the ratio of pulp cavity/tooth width (P/T ratio) in healthy cats. The dental radiographs of 32 cats (16 males and 16 females) were generated with a digital dental X-ray unit with the animals under general anesthesia. Standardized measurement of the canine teeth was performed by drawing a line on the radiograph perpendicular to the cementoenamel junction (CEJ) of the tooth. There was an inversely proportional correlation between chronological age and the P/T ratio. Moreover, a strong Pearson squared correlation (γ 2 = 0.92) was identified by the curved regression model. No significant differences in the P/T ratio based on gender or breed were found. These results suggest that determination of age by P/T ratio could be clinically useful for estimating the chronological age of cats. Keywords: age determination, age estimation, cats, dental radiograph, pulp cavity

Introduction  Dental age estimation has been widely performed in human forensic medicine and wildlife animal research. Age estimation is important for postmortem examination and has been used in human forensic medicine to determine the age of humans who died during large-scale disasters. Hard tissues, such as teeth and bones, are preserved for a long time after the soft tissues have decayed, and serve as useful evidence for personal identification [12]. The pulp cavity volume of teeth gradually decreases with age and this characteristic is known to correlate with the age-associated deposition of dentin [16]. In veterinary medicine studies of wildlife of unknown ages (grey foxes, coyotes, moose, and other

species), correlations between chronological age and teeth have been investigated [5,9,14,18]. However, few studies have involved domestic cats. The chronological age of abandoned cats is typically unknown. Therefore, it is not possible for some cat owners to know the age of the abandoned cats they have adopted.  Techniques for estimating dental age estimation are beneficial because teeth are highly resistant to mechanical, chemical, or physical trauma [1,6,8,17]. Teeth are also less affected by hormones, nutrition, and environmental factors compared to other skeletal markers [13]. Although many methods have been evaluated, dental radiography has been generally used to analyze changes of pulp cavity size in human forensic medicine and wildlife animal research [4,5,7,18]. This technique is simple, non-invasive, and suitable for age estimation [3]. The purpose of the present study was to evaluate the correlation between age and pulp cavity/tooth width ratio (P/T ratio) in healthy cats. Additionally, the relationships between P/T ratio, gender, and breed were examined.

Materials and Methods Animals  Thirty-two clinically healthy, client-owned cats in Seoul National University (Korea) (16 males and 16 females) were evaluated in this study. The age of all the cats was known and ranged from 6 to 108 months. The clients volunteered for this clinical study and signed a consent form. The breeds of the participating cats were domestic short hair (DSH; n = 17), Persian (n = 9), Turkish angora (n = 4), and Siamese (n = 2). All the cats underwent physical examination and blood testing to rule out any systemic diseases. Cats that had received dental treatment in the past were excluded from the study.

*Corresponding author: Tel: +82-2-880-1258; Fax: +82-2-883-8651; E-mail: [email protected] ⓒ 2014 The Korean Society of Veterinary Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

558 Kyoungsun Park et al.

 The entire sample population (n = 32) was used to evaluate the correlation between age and P/T ratio in healthy cats. To assess the P/T ratio according to gender and breed, the sample population was reorganized according to age. Eighteen cats were selected and evaluated based on gender (nine males and nine females) and breed (nine DSH and nine Persian). Each subgroup (n = 9) was subdivided based on age: less than 1 year old (n = 2), 1∼3 years old (n = 4), and 3∼6 years old (n = 3). To reduce statistical error, breeds that were underrepresented in the study population (Turkish Angora and Siamese cats) were excluded from the analysis (Table 1).

Anesthesia  All cats were anesthetized with medetomidine hydrochloride (40 μg/kg, Intramuscular, Domitor; Orion Pharma, Finland) and tiletamine-zolazepam (5 mg/kg, IM, Zoletil; Virbac, France). A half-dose of tiletaminezolazepam was additionally administered when the animals appeared to be recovering from anesthesia. Radiography  The cats were positioned in a sternal recumbent position for radiography of the maxillary canine teeth. These teeth were chosen for evaluation because of easily access and obdurability due to deep roots compared to other teeth. All dental radiographic images were generated with a digital dental X-ray unit (Dentix; Ardet Dental & Medical Devices, Italy). The digital sensor pad was inserted into the mouth to obtain a rostral maxillary view. The sensor pad was placed between the tongue and maxilla, and beneath the canine tooth root. The cat’s head was positioned so that the digital sensor pad was level with a position-indicating device (PID). The PID was positioned perpendicular to the bisecting angle (sensor and long axis of the tooth) as close as possible to the cat’s maxilla and over the nose as

previously described [10]. The standard exposure setting was 8 mA at 60 kVp for 0.1 sec, and the kVp setting was slightly adjusted according to the radiographic outcomes (Fig. 1).

Measurements  The radiographic images were converted into JPEG files and processed using the Adobe Photoshop CS6 image software (Adobe Systems, USA). Standardized measurements of the canine teeth were made by drawing a line on the radiograph perpendicular to the cemento-enamel junction (CEJ) of the tooth (Fig. 2). The program automatically calculated the pixel volume of the pulp cavity and tooth width using a ruler tool.  Each image file was numbered consecutively from 1 to 32

Fig. 1. Occlusal view of the maxillary canine teeth in the cat. BSA: bisecting angle.

Table 1. Demographics of the study population Breed DSH Persian Turkish Angora Siamese Total

Gender M F M F M F M F

Age (year)

tooth width ratio using dental radiography.

The purpose of this study was to evaluate the effect of age on the ratio of pulp cavity/tooth width (P/T ratio) in healthy cats. The dental radiograph...
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